Field of the Invention
The present invention relates to a paper folding apparatus to fold paper at a predetermined position and an image forming apparatus including such a paper folding apparatus. Specifically, when paper is folded by forming deflection of paper between a pair of folding rollers driven in a rotational manner, pushing the deflection part of the paper toward a nip part of the folding rollers by a pushing member driven by a drive unit, and guiding the deflection part of the paper to the nip part of the folding rollers driven in a rotational manner, even in a case where various kinds of paper having different kinds of basis weight or the like is used, it is made possible to fold the various kinds of paper at a predetermined position adequately with a simple configuration.
Description of the Related Art
In the related art, paper is folded at a predetermined position by a paper folding apparatus. For example, when a booklet or the like is formed, after an image is formed on large paper by an image forming apparatus such as a copier, the large paper is folded at a predetermined position by a paper folding apparatus.
Here, in such a paper folding apparatus, generally, a leading end of paper is carried through a gap between a pair of folding rollers. Then, the leading end of the paper is abutted on a stopper or the like and stopped at a predetermined position. Deflection is formed at a part of the paper between the pair of folding rollers and the deflection part of the paper is guided to a nip part of the pair of folding rollers driven in a rotational manner, whereby the paper is folded.
However, a shape of the deflection formed at the part of the paper between the pair of folding rollers is not fixed. For example, the shape of the deflection varies depending on a kind or basis weight of the paper or an environmental condition. In this state, when the deflection part of the paper is guided to the nip part of the pair of folding rollers driven in a rotational manner and the paper is folded, a fold position of the paper is not fixed. Specifically, there has been a problem that a fold position of thick paper having high basis weight and high stiffness and that of thin paper having low basis weight and low stiffness are different from each other.
Then, in the related art, as described in JP 2002-284443 A, the following has been proposed. That is, in a state in which a leading end of paper is abutted on a stopper or the like and is stopped at a predetermined position, deflection part of the paper is formed between a pair of folding rollers and the deflection part of the paper is guided to a nip part of the pair of folding rollers, which is driven in a rotational manner, by a bend part of a fold position regulation member.
However, in what described in JP 2002-284443 A, a relationship between a speed to form deflection of paper at a part between a pair of folding rollers and a speed to push out the deflection part of the paper toward a gap between the folding rollers by a bend part of a fold position regulation member is not considered at all.
Thus, when the speed to push out the deflection part of the paper toward the gap between the folding rollers by the bend part of the fold position regulation member becomes higher than the speed to form the deflection of the paper, there has been the following problem. That is, the paper is pushed by the bend part of the fold position regulation member and a position of a leading end of the paper abutted on a stopper or the like is shifted, and thus, a position of the paper guided to a nip part of the pair of folding rollers is shifted and it becomes not possible to fold the paper at an adequate position in the nip part of the folding rollers.
On the other hand, when the speed to form the deflection of the paper becomes higher than the speed to push out the deflection part of the paper toward the gap between the folding rollers by the bend part of the fold position regulation member, there has been the following problem. That is, before the deflection part of the paper is pushed out toward the gap between the folding rollers by the bend part of the fold position regulation member, the deflection part of the paper is guided to the nip part of the folding rollers and a position of the paper guided to the nip part of the pair of folding rollers is not fixed, and thus, it becomes not possible to fold the paper at an adequate position in the nip part of the folding rollers.
Also, in JP 2-110078 A, the following has been proposed. That is, paper carried along a carrying track through a gap between a pair of folding rollers is detected by a sensor. The result is output to a simultaneous circuit storing a folding form or the like and a redirecting mechanism is moved toward the gap between the folding rollers by controlling of rotation of a cam or the like based on the result. The paper carried along the carrying track by the redirecting mechanism is guided to the gap between the folding rollers and the paper is folded in a nip part of the folding rollers.
However, it is very difficult to perform control, by the simultaneous circuit storing a folding form or the like as described above, to move the redirecting mechanism toward the gap between the folding rollers by controlling rotation of the cam or the like and to guide the paper, which is carried along the carrying track, to an adequate fold position toward the gap between the folding rollers. Thus, a configuration to perform the control becomes complicated, and thus, there has been a problem that a cost is increased and an apparatus becomes large, for example.